Silage analysis will improve pre-lambing ewe feeding

With sheep flocks using grass silage as the base for rations in the crucial pre-lambing period, Rosie Miller, Ruminant Specialist with Trouw Nutrition GB stresses the importance of getting silage for pregnant sheep analysed.

January 2018

“Managing ewe nutrition in the run up to lambing is an important step toward a successful lamb crop, influencing lambing ease, lamb survival and vigour and milk yield and growth,” she comments. “Trying to achieve this accurately and cost-effectively without a representative silage analysis and a clear picture of the nutritional content of the forage will be extremely difficult.

“The starting point of any ration is good quality forage, with compound feed or straights fed alongside. To develop an effective diet you have to know how good the forage is so that the other feeds supplement it correctly to meet the total requirements of the ewe. You won’t know this just by opening the bale and visually assessing the forage

“Forage is an important part of pre-lambing diets at what is a crucial stage for the ewe and the lamb crop,” she continues. “Assuming an average analysis as the basis for supplementation decisions could result in ewes being either over-fed or underfed.”

An analysis of sheep silages carried out last year by Trouw Nutrition GB showed a significant range in energy supply with the average sheep silage analysing at 9.8MJ/kgDM with the best silages coming in at 10.8MJ/kgDM. This difference will impact on supplementation levels and performance.

“Not only is the energy content of the top silages higher, but the better quality means ewes will eat more, further increasing the total energy from forage and reducing the extent of supplementation required.

“With a 9.8MJ silage, a 70kg ewe in the three weeks pre-lambing would consume 1.2% of bodyweight or 0.84kgDM of silage per day. If a 10.8MJ silage is available the same ewe could consume 1.4% of bodyweight, equivalent to 0.98kgDM of silage per day.

“Both ewes would have an energy requirement of 15.3MJ per day, but while the ewe on poor silage would derive 7.6MJ from forage, the ewe on the better silage would be getting 10.8MJ from silage which makes a big difference to the level of concentrates required.

“Assuming an 11.8MJ concentrate, the ewe on good silage would require 0.43kg freshweight of concentrates to meet her requirements, while the ewe on poor forage would need 0.60kg freshweight of concentrates, an increase of 0.17kg/day.”

Ms Miller says that without an analysis of the forage, the level of concentrates to feed will be an estimate rather that a calculated amount. This can have a significant impact on performance. With a significant proportion of lamb losses occurring at and immediately post lambing, getting nutrition right can have a big impact on profitability.

“Using our example, if the farmer assumed he was using average quality silage and supplemented accordingly but actually had the better quality feed, ewes would be being overfed by 170g/day. For a 350 ewe flock this is 60kg of concentrates per day that is being fed unnecessarily at a cost of around £13 per day. As well as pushing up costs, there is a risk of overweight lambs and more problems at lambing.”She comments that the consequence of over-feeding ewes will be higher feed costs and a range of potential problems. Overfed or fat ewes face an increased risk of twin lamb disease, dystocia and prolapse. They will also have decreased feed intakes post-lambing which will affect milk production and lamb growth.

Underfeeding means ewes may lose excess body condition and they will be more likely to give birth to lighter lambs. They will have poorer colostrum quality and yields and reduced milk yields all of which will compromise early lamb growth and increase mortality.

Ms Miller says many sheep farmers have been put off having silage analysed because the typical silage analysis report is tailored for dairy farmers and contains a lot of parameters which are not relevant to sheep rationing. Trouw Nutrition GB now produce a special analysis report especially for sheep farmers which provides the information they require such as metabolisable protein levels, and is available through the farm’s feed supplier.

“Samples can be analysed and back on farm in a few days meaning diets can be reviewed and fine-tuned to improve performance and control costs. To ensure they get the correct analysis, farmers should write ’sheep’ on the analysis request form.

“Investing time in getting silage analysed could make a big difference to performance and margins this winter, and make for a less stressful lambing time,” Ms Miller observes.